Scattered Pilot Pattern And Channel Estimation Method For MIMO-OFDM Systems

1. A method of inserting pilot symbols into Orthogonal Frequency Division Multiplexing (OFDM) frames at an OFDM transmitter having at least two pairs of transmitting antennas, the OFDM frames having a time domain and a frequency domain, the method comprising: for each antenna, sparsely distributing pilot symbols in a respective pattern in time-frequency, the patterns being identical for each pair of antennas, and a pilot density for a first pair of the two pairs of transmitting antennas is higher than a pilot density for a second pair of the two pairs of transmitting antennas; and for each antenna, transmitting the sparsely distributed pilot symbols.

2. The method of claim 1 , wherein at least one pattern is offset from a pilot pattern of an adjacent base station.

3. The method of claim 1 , further comprising, for the first antenna of each pair of antennas, inserting pilot symbols in a respective first scattered pattern in time-frequency and inserting null symbols in a respective second scattered pattern in time-frequency; and for a second antenna of each pair of antennas, inserting pilot symbols in the respective second scattered pattern in time-frequency and inserting null symbols in the respective first scattered pattern in time-frequency.

4. The method of claim 1 , further comprising transmitting the pilot symbols at a higher power level than data symbols.

5. An Orthogonal Frequency Division Multiplexing (OFDM) base station of a wireless network, the OFDM base station having at least two pairs of transmitting antennas configured to transmit pilot symbols in OFDM frames, the OFDM frames having a time domain and a frequency domain, the base station configured to: for each antenna, sparsely distribute pilot symbols in a respective pattern in time-frequency, the patterns being identical for each pair of antennas, and a pilot density for a first pair of the two pairs of transmitting antennas is higher than a pilot density for a second pair of the two pairs of transmitting antennas; and for each antenna, transmit the sparsely distributed pilot symbols.

6. The OFDM base station of claim 5 , wherein at least one pattern is offset from a pilot pattern of an adjacent base station.

7. The OFDM base station of claim 5 , further configured to insert, for the first antenna of each pair of antennas, pilot symbols in a respective first scattered pattern in time-frequency and inserting null symbols in a respective second scattered pattern in time-frequency; and for a second antenna of each pair of antennas, inserting pilot symbols in the respective second scattered pattern in time-frequency and inserting null symbols in the respective first scattered pattern in time-frequency.

8. The OFDM base station of claim 5 , further configured to transmit the pilot symbols at a higher power level than data symbols.

9. A non-transitory computer readable medium for inserting pilot symbols into Orthogonal Frequency Division Multiplexing (OFDM) frames at an OFDM transmitter having at least two pairs of transmitting antennas, the OFDM frames having a time domain and a frequency domain, the computer readable medium storing instructions to cause a processor to perform operations comprising: for each antenna, sparsely distributing pilot symbols in a respective pattern in time-frequency, the patterns being identical for each pair of antennas, and a pilot density for a first pair of the two pairs of transmitting antennas is higher than a pilot density for a second pair of the two pairs of transmitting antennas; and for each antenna, transmitting the sparsely distributed pilot symbols.

10. The non-transitory computer readable medium of claim 9 , wherein at least one pattern is offset from a pilot pattern of an adjacent base station.

11. The non-transitory computer readable medium of claim 9 , further comprising for the first antenna of each pair of antennas, inserting pilot symbols in a respective first scattered pattern in time-frequency and inserting null symbols in a respective second scattered pattern in time-frequency; and for a second antenna of each pair of antennas, inserting pilot symbols in the respective second scattered pattern in time-frequency and inserting null symbols in the respective first scattered pattern in time-frequency.

12. The non-transitory computer readable medium of claim 9 , further comprising transmitting the pilot symbols at a higher power level than data symbols.